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From:   Horia Geanta <horia.geanta@nxp.com>
To:     Andrey Smirnov <andrew.smirnov@gmail.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>
CC:     Chris Healy <cphealy@gmail.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Iuliana Prodan <iuliana.prodan@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH v6 6/7] crypto: caam - enable prediction resistance in
 HRWNG
Thread-Topic: [PATCH v6 6/7] crypto: caam - enable prediction resistance in
 HRWNG
Thread-Index: AQHVxjouh/c8xz5csUKnQ9CkhtEExg==
Date:   Tue, 21 Jan 2020 06:20:10 +0000
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 <20200108154047.12526-7-andrew.smirnov@gmail.com>
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On 1/20/2020 6:38 PM, Horia Geanta wrote:=0A=
> On 1/8/2020 5:42 PM, Andrey Smirnov wrote:=0A=
>> @@ -275,12 +276,25 @@ static int instantiate_rng(struct device *ctrldev,=
 int state_handle_mask,=0A=
>>  		return -ENOMEM;=0A=
>>  =0A=
>>  	for (sh_idx =3D 0; sh_idx < RNG4_MAX_HANDLES; sh_idx++) {=0A=
>> +		const u32 rdsta_if =3D RDSTA_IF0 << sh_idx;=0A=
>> +		const u32 rdsta_pr =3D RDSTA_PR0 << sh_idx;=0A=
>> +		const u32 rdsta_mask =3D rdsta_if | rdsta_pr;=0A=
>>  		/*=0A=
>>  		 * If the corresponding bit is set, this state handle=0A=
>>  		 * was initialized by somebody else, so it's left alone.=0A=
>>  		 */=0A=
>> -		if ((1 << sh_idx) & state_handle_mask)=0A=
>> -			continue;=0A=
>> +		if (rdsta_if & state_handle_mask) {=0A=
>> +			if (rdsta_pr & state_handle_mask)=0A=
>> +				continue;=0A=
>> +=0A=
>> +			dev_info(ctrldev,=0A=
>> +				 "RNG4 SH%d was previously instantiated without prediction resistan=
ce. Tearing it down\n",=0A=
>> +				 sh_idx);=0A=
>> +=0A=
>> +			ret =3D deinstantiate_rng(ctrldev, rdsta_if);=0A=
>> +			if (ret)=0A=
>> +				break;=0A=
> In case state handle 0 is deinstantiated, its reinstantiation with PR sup=
port=0A=
> will have the side effect of re-generating JDKEK, TDKEK, TDSK.=0A=
> This needs to be avoided, since other SW components (like OP-TEE f/w)=0A=
> could have black keys in use. Overwriting the KEK registers would no long=
er=0A=
> allow CAAM to decrypt them.=0A=
> =0A=
Never mind, looks like there is logic in place to check whether=0A=
keys have been generated or not, by looking at RDSTA[SKVN].=0A=
=0A=
Horia=0A=